A baby walker is a kind of children's apparatus having an upper frame (bracket table) and a lower frame (chassis) with wheels. A baby seat is hung under the bracket table. The conventional baby walker has no height-adjustment mechanism and its height can be adjusted only by the stepped sections on the seat frame. As people's living standards are improved, they demand a height-adjustment mechanism (the lifting gear) for a baby walker which not only fits the height of each baby but also adjusted to the the growth of a baby. Some conventional baby walkers use a crossed rod support for a height adjustment gear which can control the included angle of the cross-rod by means of a ratchet down slot under the bracket table to position and control the height of the baby walker.